Display screen or portion thereof with transitional graphical user interface



FIG. 1 is the first image in a sequence for a display screen or portion thereof with transitional graphical user interface showing our new design;

FIG. 2 is the second image thereof;

FIG. 3 is the third image thereof;

FIG. 4 is the fourth image thereof;

FIG. 5 is the fifth image thereof;

FIG. 6 is the sixth image thereof;

FIG. 7 is the seventh image thereof; and,

FIG. 8 is the eighth image thereof.

The outermost broken lines in the Figures illustrate a display screen or portion thereof. The remainder of the broken lines within the Figures illustrate portions of the transitional graphical user interface. None of the broken lines form part of the claimed design.

The appearance of the transitional image sequentially transitions between the images shown in FIGS. 1-8. The process or period in which one image transitions to another image forms no part of the claimed design. 

CLAIM The ornamental design for a display screen or portion thereof with transitional graphical user interface, as shown and described. 